1a. Objectives (from AD-416):
The goal of this research will be to obtain knowledge and develop tools that will enable planners, decision makers, and producers to more effectively manage, conserve, and protect water resources. Specific objectives are as follows: 1)Develop cotton and peanut production systems for humid areas that are based on site-specific water and nutrient applications, 1a)Develop water management strategies in humid areas that optimize spatial and temporal water applications, 1b)Develop and explore spatial nutrient management for irrigated and non-irrigated crops in humid areas; 2)Develop practices that increase crop water use efficiency in rainfed/irrigated cropping systems in relation to tillage, irrigation, and crop management practices; and 3) Develop practices and technologies that enhance denitrification and expand the knowledge of microbial communities including their genetics and implication on geospecific disease in riparian buffers, wetlands, and streams for improving water quality.
1b. Approach (from AD-416):
This 5-year project utilizes a systems approach to identify and develop strategies for improved spatial management of water and nutrients. The project explores the spatial components of irrigation, tillage, and nutrient management. In spatial irrigation, the project will focus on identifying strategies for managing a site-specific irrigation system to conserve water and nutrients while maintaining cost effective production. In tillage management, the project will focus on efficiency of water use using tillage practices that will improve infiltration and soil water-holding capacities under site-specific irrigation to determine the spatial uptake and water use efficiency to improve spatial water management. In nutrient management, the project will focus on both in-field and off-site management. In-field nutrient management will focus on spatial nitrogen applications on cotton and Coastal bermudagrass to improve crop production and reduce the impact of off-site nitrogen movement. Off-site nitrogen and water management will focus on understanding the geospatial variability of microbial communities along with nitrous oxide emissions from riparian buffers, wetlands, and streams. In Objective 3, the Experimental Approach is altered to expand the sites under the Denitrification Enzyme Activity section and delete the Treatment Wetland Microcosms section.
3. Progress Report:
This is the final report for project 6657-13000-008-00D, which terminated in December 2011. Follow-on research continues under new project 6657-13000-009-00D. Variable Rate Irrigation: Under objective 1, Corn was grown using site-specific water and fertilizer applications. Irrigated yield response to nitrogen was quadratic while rainfed yield response was linear. These yield responses will be helpful in developing management strategies for profitable spatial water and nitrogen management. To obtain spatial data for irrigation management data during the growing season, we evaluated crop vegetation and canopy temperatures. Vegetative reflectance sensors determined spatial canopy biomass and could be effective in determining site specific plant water needs while infra-red thermometers identified areas under water stress and could be used to initiate irrigations. These results can help farmers manage variable rate irrigation systems. In site-specific agriculture, spatial crop responses are important, so a statistical methodology was developed to explain the variations and estimate uncertainty in the results. This new statistical methodology provided a tool to better account for spatial variation. Conservation tillage: Climate prediction models indicate that the southeastern U.S. will experience more frequent drought. During drought years, we observed under objective 2 that conservation tillage increased cotton yields by 25% over conventional tillage. These results will be used in developing improved cotton production practices that ensure sustainable production in a changing climate. Bioenergy and water: Under objective 2, we investigated climate and weather impacts on water along with bioenergy crop production. Planners must assess water availability as well as potential bioenergy crop water use to avoid supply disruptions. Improved crops, water management, recycled water, and new technologies for bioenergy conversion offer opportunities for bioenergy sustainably. Subsurface Drip Irrigation: Under objective 1, a subsurface drip irrigation system was installed for treated effluent application to bermudagrass hay. The plots receiving treated effluent had significantly greater hay yields and greater nutrient removal than the commercial fertilizer plots. Additionally, we found that the irrigation system produced adequate quality hay for ruminant production. Hay grown with effluent also had greater energy content per hectare. These results demonstrated that a subsurface drip irrigation system for treated effluent application can produce quality hay forage and bioenergy while protecting the environment. Riparian Buffers: Under objective 2, we characterized the microbial community in a riparian buffer adjacent to areas receiving heavy nitrate loads because they have a higher propensity for nitrous oxide emission. A correlation was identified between Proteobacteria and both complete and incomplete denitrification. Identifying and propagation of microorganisms capable of complete nitrification have the potential to improve riparian buffers and reduce nitrate pollution and greenhouse gas emissions.
1. Analysis of stroke rate and soil hydric factors in coastal plain soils. In the United States, stroke rates have dropped since the 1930’s except in the Southeast. This region, which includes the southeastern Coastal Plain region of North and South Carolina and Georgia, forms what is now known as the "Buckle of the Stroke Belt." People born within this region have higher rates of stroke, even after they migrate to other regions of the country. To determine if there was a link between soil properties and stroke rates, we correlated measurements of South Carolina soil characteristics obtained from the Natural Resources Conservation Service’s Soil Survey Geographic database to regional stroke mortality rates. Relationships between several soil water measures including depth to water table, drainage class, and hydric rating to South Carolina stroke rate were demonstrated. This report results in the opening of a new frontier to determine the role of soil and water characteristics in human health.
2. Irrigated bermudagrass production in the southeastern U.S. In the Southeast U.S., sustainable hay production for the cattle industry is needed to alleviate water deficit stress during the short periods of drought that are common in the region. In this study, we investigated the impact of irrigation management practices and nitrogen fertility levels on Tifton 85 bermudagrass yield and forage quality. We evaluated four irrigation rates designed to alleviate water deficit stress, three nitrogen fertilization rates for each irrigation rate, and harvested at four- and eight-week intervals. We also found that during harvest intervals without sufficient rainfall to maintain adequate soil moisture levels, hay yields increased linearly with irrigation rate. These harvests also had significant forage quality trends with increasing irrigation rate. Additionally, for the non-irrigated treatments, we observed that hay yields decreased linearly as the soil moisture was depleted. Irrigation management to maintain acceptable soil moisture can sustain and potentially increase bermudagrass hay production in the southeastern Coastal Plain.
Hunt, P.G., Stone, K.C., Matheny, T.A., Vanotti, M.B., Szogi, A.A., Busscher, W.J. 2011. Double-cropped soybean and wheat with subsurface drip irrigation supplemented by treated swine wastewater. Communications in Soil Science and Plant Analysis. 42:2778-2794.